Add support for RSS feeds

src/main/java/me/mrletsplay/mdblog/MdBlog.java

@@ -22,6 +22,10 @@ import me.mrletsplay.mdblog.blog.Post;
 import me.mrletsplay.mdblog.blog.PostMetadata;
 import me.mrletsplay.mdblog.markdown.MdParser;
 import me.mrletsplay.mdblog.markdown.MdRenderer;
+import me.mrletsplay.mdblog.rss.FeedConfig;
+import me.mrletsplay.mdblog.rss.RSSFeed;
+import me.mrletsplay.mdblog.rss.RSSItem;
+import me.mrletsplay.mdblog.rss.RSSResponse;
 import me.mrletsplay.mdblog.template.Template;
 import me.mrletsplay.mdblog.template.Templates;
 import me.mrletsplay.mdblog.util.PostPath;
@@ -30,6 +34,7 @@ import me.mrletsplay.mrcore.http.HttpUtils;
 import me.mrletsplay.simplehttpserver.dom.html.HtmlDocument;
 import me.mrletsplay.simplehttpserver.dom.html.HtmlElement;
 import me.mrletsplay.simplehttpserver.http.HttpRequestMethod;
+import me.mrletsplay.simplehttpserver.http.HttpStatusCodes;
 import me.mrletsplay.simplehttpserver.http.document.FileDocument;
 import me.mrletsplay.simplehttpserver.http.request.HttpRequestContext;
 import me.mrletsplay.simplehttpserver.http.server.HttpServer;
@@ -40,12 +45,17 @@ public class MdBlog {
 		FILES_PATH = Path.of("files"),
 		POSTS_PATH = FILES_PATH.resolve("posts");
 
+	private static final String
+		FEED_NAME = "feed.xml",
+		FEED_CONFIG_NAME = "feed.txt";
+
 	private static HttpServer server;
 	private static WatchService watchService;
 	private static List<WatchKey> watchedDirectories;
 	private static Map<PostPath, Post> posts;
 	private static Map<PostPath, Templates> indexTemplates;
 	private static Map<PostPath, FileDocument> globalResources;
+	private static Map<PostPath, FeedConfig> feedConfigs;
 
 	private static Templates defaultTemplates;
 
@@ -56,6 +66,7 @@ public class MdBlog {
 			.create());
 
 		server.getDocumentProvider().register(HttpRequestMethod.GET, "/", () -> createPostsIndex(PostPath.root()));
+
 		server.getDocumentProvider().registerPattern(HttpRequestMethod.GET, "/{path...}", () -> handleRequest(HttpRequestContext.getCurrentContext()));
 
 		defaultTemplates = new Templates(null);
@@ -74,6 +85,7 @@ public class MdBlog {
 		posts = new HashMap<>();
 		indexTemplates = new HashMap<>();
 		globalResources = new HashMap<>();
+		feedConfigs = new HashMap<>();
 
 		extractAndRegister("style/base.css");
 		extractAndRegister("style/index.css");
@@ -105,7 +117,7 @@ public class MdBlog {
 
 		// Generate posts index
 		List<PostPath> allPaths = posts.keySet().stream()
-			.filter(p -> path == null || (p.startsWith(path) && !p.equals(path)))
+			.filter(p -> p.startsWith(path) && !p.equals(path))
 			.map(p -> path == null ? p : p.subPath(path.length()))
 			.toList();
 
@@ -191,6 +203,25 @@ public class MdBlog {
 			return;
 		}
 
+		if(path.getName().equals(FEED_NAME)) {
+			PostPath blogPath = path.getParent();
+			FeedConfig config = feedConfigs.get(blogPath);
+			if(config != null) {
+				boolean recursive = ctx.getRequestedPath().getQuery().getFirst("recursive", "false").equals("true");
+
+				RSSFeed feed = new RSSFeed(config.title(), config.link(), config.description());
+
+				posts.entrySet().stream()
+					.filter(e -> e.getKey().startsWith(blogPath) && (recursive || e.getKey().length() == path.length()))
+					.forEach(e -> {
+						Post p = e.getValue();
+						feed.addItem(new RSSItem(p.getMetadata().title(), p.getMetadata().author(), config.link() + "/" + e.getKey().subPath(blogPath.length()), p.getMetadata().description()));
+					});
+				ctx.respond(HttpStatusCodes.OK_200, new RSSResponse(feed));
+				return;
+			}
+		}
+
 		Post post = posts.get(path);
 
 		if(post != null) {
@@ -247,8 +278,8 @@ public class MdBlog {
 	}
 
 	private static void updateBlogs() throws IOException {
-		System.out.println("Update");
 		indexTemplates.clear();
+		feedConfigs.clear();
 
 		Files.walk(POSTS_PATH)
 			.filter(Files::isRegularFile)
@@ -273,6 +304,18 @@ public class MdBlog {
 				} catch (IOException e) {}
 			});
 
+		Files.walk(POSTS_PATH)
+			.filter(Files::isRegularFile)
+			.filter(f -> f.getFileName().toString().equals(FEED_CONFIG_NAME))
+			.forEach(f -> {
+				try {
+					PostPath path = PostPath.of(POSTS_PATH.relativize(f).getParent());
+					String configString = Files.readString(f, StandardCharsets.UTF_8);
+					FeedConfig config = FeedConfig.load(configString);
+					feedConfigs.put(path, config);
+				}catch(IOException e) {}
+			});
+
 		Iterator<Map.Entry<PostPath, Post>> it = posts.entrySet().iterator();
 		while(it.hasNext()) {
 			Map.Entry<PostPath, Post> en = it.next();

src/main/java/me/mrletsplay/mdblog/rss/FeedConfig.java

@@ -0,0 +1,31 @@
+package me.mrletsplay.mdblog.rss;
+
+public record FeedConfig(String title, String description, String link) {
+
+	public static FeedConfig load(String configString) {
+		String title = "Untitled Blog";
+		String description = "No description";
+		String link = "http://localhost";
+
+		for(String line : configString.split("\n")) {
+			if(line.isBlank()) continue;
+			String[] spl = line.split(":", 2);
+			if(spl.length != 2) {
+				System.err.println("Invalid config line: " + line);
+				continue;
+			}
+
+			String key = spl[0].toLowerCase().trim();
+			String value = spl[1].trim();
+
+			switch(key) {
+				case "title" -> title = value;
+				case "description" -> description = value;
+				case "link" -> link = value;
+			}
+		}
+
+		return new FeedConfig(title, description, link);
+	}
+
+}

src/main/java/me/mrletsplay/mdblog/rss/RSSFeed.java

@@ -0,0 +1,78 @@
+package me.mrletsplay.mdblog.rss;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import javax.xml.parsers.DocumentBuilder;
+import javax.xml.parsers.DocumentBuilderFactory;
+import javax.xml.parsers.ParserConfigurationException;
+
+import org.w3c.dom.Document;
+import org.w3c.dom.Element;
+
+public class RSSFeed {
+
+	private String title;
+	private String link;
+	private String description;
+	private List<RSSItem> items;
+
+	public RSSFeed(String title, String link, String description) {
+		this.title = title;
+		this.link = link;
+		this.description = description;
+		this.items = new ArrayList<>();
+	}
+
+	public void addItem(RSSItem item) {
+		items.add(item);
+	}
+
+	public Document toXML() throws ParserConfigurationException {
+		DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
+		DocumentBuilder builder = dbf.newDocumentBuilder();
+		Document doc = builder.newDocument();
+
+		Element rss = doc.createElement("rss");
+		doc.appendChild(rss);
+
+		Element channel = doc.createElement("channel");
+		rss.appendChild(channel);
+
+		Element title = doc.createElement("title");
+		title.setTextContent(this.title);
+		channel.appendChild(title);
+
+		Element link = doc.createElement("link");
+		link.setTextContent(this.link);
+		channel.appendChild(link);
+
+		Element description = doc.createElement("description");
+		description.setTextContent(this.description);
+		channel.appendChild(description);
+
+		for(RSSItem item : items) {
+			Element itemEl = doc.createElement("item");
+			channel.appendChild(itemEl);
+
+			Element itTitle = doc.createElement("title");
+			itTitle.setTextContent(item.title());
+			itemEl.appendChild(itTitle);
+
+			Element itAuthor = doc.createElement("author");
+			itAuthor.setTextContent(item.author());
+			itemEl.appendChild(itAuthor);
+
+			Element itLink = doc.createElement("link");
+			itLink.setTextContent(item.link());
+			itemEl.appendChild(itLink);
+
+			Element itDescription = doc.createElement("description");
+			itDescription.setTextContent(item.description());
+			itemEl.appendChild(itDescription);
+		}
+
+		return doc;
+	}
+
+}

src/main/java/me/mrletsplay/mdblog/rss/RSSItem.java

@@ -0,0 +1,5 @@
+package me.mrletsplay.mdblog.rss;
+
+public record RSSItem(String title, String author, String link, String description) {
+
+}

src/main/java/me/mrletsplay/mdblog/rss/RSSResponse.java

@@ -0,0 +1,49 @@
+package me.mrletsplay.mdblog.rss;
+
+import java.io.ByteArrayOutputStream;
+
+import javax.xml.parsers.ParserConfigurationException;
+import javax.xml.transform.OutputKeys;
+import javax.xml.transform.Transformer;
+import javax.xml.transform.TransformerException;
+import javax.xml.transform.TransformerFactory;
+import javax.xml.transform.TransformerFactoryConfigurationError;
+import javax.xml.transform.dom.DOMSource;
+import javax.xml.transform.stream.StreamResult;
+
+import org.w3c.dom.Document;
+
+import me.mrletsplay.simplehttpserver.http.response.HttpResponse;
+import me.mrletsplay.simplehttpserver.http.util.MimeType;
+
+public class RSSResponse implements HttpResponse {
+
+	private RSSFeed feed;
+
+	public RSSResponse(RSSFeed feed) {
+		this.feed = feed;
+	}
+
+	@Override
+	public byte[] getContent() {
+		try {
+			Document doc = feed.toXML();
+			Transformer transform = TransformerFactory.newInstance().newTransformer();
+			transform.setOutputProperty(OutputKeys.INDENT, "yes");
+			transform.setOutputProperty(OutputKeys.METHOD, "xml");
+			transform.setOutputProperty(OutputKeys.ENCODING, "UTF-8");
+			transform.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", "4");
+			ByteArrayOutputStream bOut = new ByteArrayOutputStream();
+			transform.transform(new DOMSource(doc), new StreamResult(bOut));
+			return bOut.toByteArray();
+		} catch (TransformerException | TransformerFactoryConfigurationError | ParserConfigurationException e) {
+			throw new RuntimeException(e);
+		}
+	}
+
+	@Override
+	public MimeType getContentType() {
+		return MimeType.of("application/rss+xml");
+	}
+
+}